What to do

My friend told me that him and his wife have this agreement where they can sleep with one person of their choice and not get into trouble with the spouse. He told me that I was his. Mind you we are both married and I’m happily married. He said his work might transfer him up here (he lives out of state currently). I think my husband would be happy with him being able to sleep with one person and not getting into trouble but at the same time we are happy together and don’t want to mess anything up. We have both been hurt and cheated on in the past. Do I bring it up to my husband or do I leave it alone? I don’t want to sleep with anyone else but my husband and I love him to death but I think he would be happy that we he can have sex when I’m on my period.